Make sure that you have Backup Accounts enabled in Home » Backup » Configure Backup, or your accounts will not be backed up. This is explained in the documentation Infopro linked to, but frequently overlooked.

You can start a backup at any time by running this command as root:

Code:

# /scripts/cpbackup --force

If you install the cronconfig plugin, in Home » cPanel » Manage Plugins, then log out of the WebHost Manager and log back in, you will see a new menu item: Home » Plugins » Configure cPanel Cron Times. This will let you set the time of day that the cPanel backup system runs. Most administrators choose to run it late at night, because it can generate some server load.

It looks like you have incremental backups enabled. Incremental backups only back up what has changed since an initial backup. If nothing has changed in an account, the process will finish very quickly.